In recent years, there has been investigation into performing Fast Cell Selection (FCS) whereby, when a mobile station apparatus is located in an area near the boundaries of a plurality of cells or sectors (hereinafter referred to as a “handover area”), a base station apparatus or antenna constituting a communicating party is switched over at high speed in a short time cycle, such as a slot, for example, in response to instantaneous reception level fluctuation (see Non-patent Document 1, for example).
FIG. 1A is a drawing showing an example of a base station apparatus selection operation by means of FCS. As shown in this figure, a mobile station apparatus 10 is switching its communicating party between a base station apparatus 20 and a base station apparatus 30 in order from first slot 40.
To be specific, mobile station apparatus 10 receives common pilot channel signals (hereinafter referred to as “common pilot signals”) transmitted from base station apparatus 20 and base station apparatus 30, and measures the reception SIR (Signal to Interference Ratio). The results of this measurement are shown in FIG. 1B. In this figure, the solid line shows the reception SIR of the signal from base station apparatus 20, and the dotted line shows the reception SIR of the signal from base station apparatus 30.
Then mobile station apparatus 10 selects the base station apparatus whose reception SIR is larger on a slot-by-slot basis, and transmits information relating to the selected base station apparatus to base station apparatus 20 and base station apparatus 30. The slot-by-slot selected base station apparatus in this case is shown by a solid line (that is, base station apparatus 20) or dotted line (that is, base station apparatus 30) at the bottom of FIG. 1B.
Base station apparatus 20 and base station apparatus 30 receive information relating to the selected base station apparatus from mobile station apparatus 10, and the slot-by-slot selected base station apparatus transmits a dedicated channel, high-speed packet channel, or suchlike data signal (hereinafter referred to as “dedicated data signal”) in the slots indicated by hatching in FIG. 1A.
Having mobile station apparatus 10 located in a handover area switch the selected base station apparatus in a short time cycle such as a slot in this way enables mobile station apparatus 10 reception quality and throughput to be improved.
Also, Patent Document 1, for example, describes a technology whereby base station apparatuses report the amount of traffic, and a mobile station apparatus located in a handover area switches the selected base station apparatus based on the amount of traffic reported from each base station apparatus.
Non-patent Document 1: “Physical layer aspects of UTRA High Speed Downlink Packet Access” (section 6.4), 3GPP TR25.848 V4.4.0 (2001-03)
Patent Document 1: Unexamined Japanese Patent Publication No. 2003-264869